Boolean difference adding
You have some overlapping vertices in your letter. These break the boolean. Your normals are also inside out and should be flipped.
Merge by Distance

Select your cutter and toggle to Edit Mode Tab. Press A to select all. Under Mesh tab select Clean Up and Merge by Distance.

Recalculate Normals

From Viewport Overlays panel you can check Face Orientation checkbox. This lets you see which way your normals are facing. Blue should be outside and red should be inside.

To recalculate the normals select your object toggle to Edit Mode. Select all and Under Mesh tab choose Normals and Recalculate Outside. You should do this to both of your objects.